Water Electrolysis

Hydrogen Gas (H2)

Hydrogen gas is lighter than air and, as a result, it rises in the atmosphere. This is why hydrogen as a gas (H2) is not found by itself on earth. It is found only in compound form with other elements. Hydrogen combined with oxygen, is water (H2O). Hydrogen combined with carbon, forms different compounds such as methane (CH4), coal, and petroleum. Hydrogen is also found in all growing things—biomass. It is also an abundant element in the earth’s crust.

Hydrogen has the highest energy content of any common fuel by weight (about three times more than gasoline), but the lowest energy content by volume (about four times less than gasoline). It is the lightest element, and it is a gas at normal temperature and pressure.

Since hydrogen doesn’t exist on earth as a gas, we must separate it from other elements. We can separate hydrogen atoms from water, biomass, or natural gas molecules. The two most common methods for producing hydrogen are steam reforming and electrolysis (water splitting). Scientists have even discovered that some algae and bacteria give off hydrogen.

• Steam reforming is currently the least expensive method of producing hydrogen and accounts for about 95 percent of the hydrogen produced in the United States. It is used in industries to separate hydrogen atoms from carbon atoms in methane(CH4). Because methane is a fossil fuel, the process of steam reforming results in greenhouse gasemissions that are linked with global warming.

• Electrolysis is a process that splits hydrogen from water. It results in no emissions but it is currently a very expensive process. New technologies are being developed all the time.